Apparatus and method for cleaning a surgically prepared bone surface

ABSTRACT

An apparatus suitable for cleaning a surgically prepared working surface comprises a body portion adapted to supply pressurized fluid (preferably carbon dioxide gas) to the surgically prepared working surface and aspirate surface debris dislodged from the surgically prepared working surface. The apparatus further comprises a head portion adapted to constrain the supplied pressurized fluid to flow substantially along the surgically prepared working surface to dislodge debris there from when the head portion is in contact with the surgically prepared working surface. The dislodged surface debris are aspirated by the body portion.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates generally to surgical instruments, and more particularly to apparatus and method for cleaning a surgically prepared working surface.

2. Description of the Related Art

In traditional orthopedic surgery, bone is prepared to receive a prosthetic implant by first cutting or sculpting the bone with a manual or powered tool such as a saw, drill, or broach. Next, the exposed bone is usually cleaned with a sterile saline solution for lavage and irrigation. Finally, suction is applied to remove debris. Often, surgical sponges are inserted into a cavity or against the bone surface to absorb excess fluids.

Joint replacements are commonly but not necessarily secured with the aid of “joint cement” or biocompatible adhesives. A typical such cement is a polymethyl methacrylate. The success of such adhesives is thought to depend in part on proper preparation of the bone bed.

U.S. Pat. No. 5,037,437 to Matsen III (1991) discloses a significant improvement in the art of preparing bone surface for cemented joint replacement surgery. Matsen identified some of the previously unrecognized shortcomings of traditional liquid flushing lavage for preparation of the cancellous portions of an exposed bone bed. Matsen's invention was based on the finding that dry flowing gas directed at and into the sculpted bony bed effectively prepares the bone for prosthetic implantation. When a bone cement is also used, the use of gas increases the likelihood of strong mechanical interdigitation of the bone cement with the bone. A number of such advantages to the gas lavage technique are identified in U.S. Pat. No. 5,037,437; the enumerated advantages need not be repeated here. Additional advantages may exist which have not been identified. Matsen also suggests that carbon dioxide is especially well suited for use as the dry gas for bone lavage, being demonstrated safe for use in the human body. As he notes, “the very high diffusion coefficient of carbon dioxide causes it to present a significantly lower risk of embolism as compared to the use of nitrogen or oxygen.” Moreover, carbon dioxide gas is commonly available in hospital operating rooms, finding use in laparascopic surgery, for example.

Since the publication of the Matsen patent, tools have become available for preparing bony surfaces by sterile, dry gas lavage, or lavage with sterile admixtures of gas and liquid. A carbon dioxide lavage system is available, for example, from Kinamed, Inc. in Camarillo, Calif. (marketed under the trade name “CarboJet”). The use of carbon dioxide is believed to be more effective than liquid debris removal because a compressed gas jet creates strong, fluctuating pressure gradients, displacing debris rapidly and thoroughly. This method is more effective at removing fluid and fluid-suspended debris from the interstices of cancellous bone.

Although surgical gas lavage nozzles are available, typical nozzles must be used in concert with surgical suction tools. Simultaneous manipulation and coordination of both gas supply and suction is difficult. Flow of the gas is not well controlled or confined to the bony surface. Both suction and gas jet must be constantly moved in a drying pattern to effectively clean and dry the bony surface. The difficulty of this technique in increased in surgical situations that permit only limited access or interfere with the surgeon's freedom of motion. As one example, in knee replacement surgery several planar bone cuts are commonly made in the femur and tibia. It is desirable to prepare these surfaces to receive prosthetics.

Many surgeons are currently employing a “minimally invasive” surgical technique for knee replacement, which involves making only a very small incision at the front of the knee. The very small incision does not permit full freedom to access the cut bone surfaces from any arbitrary angle. In fact, a gap of less than 12 millimeters may be accessible between the prepared femur and tibia surfaces. In some cases, a gap as small as 8 millimeters may be present. Conventional gas jet instruments and suction instruments are not well suited to access the planar cuts in the knee without more exposure than that offered in minimally invasive surgical techniques.

A need persists for specially adapted lavage devices and methods which can better access bony surfaces, and which more efficiently and conveniently prepare the surfaces to receive cement or implants. Any time saved in the operating room is of great value (medically and economically) to both surgeon and patient.

SUMMARY OF THE INVENTION

In accordance with one aspect of the invention, an apparatus suitable for cleaning a surgically prepared working surface comprises means for supplying pressurized fluid to the surgically prepared working surface, at least one surface debris aspirator operatively coupled to the pressurized fluid supply means, and means for constraining the supplied pressurized fluid to flow substantially along the surgically prepared working surface. The constrained fluid flow forcibly cleans the surgically prepared working surface of biological fluids and debris.

In accordance with another aspect of the invention, an apparatus suitable for cleaning a surgically prepared working surface comprises means for supplying pressurized fluid to the surgically prepared working surface, at least one surface debris aspirator operatively coupled to the pressurized fluid supply means, and means for constraining the supplied pressurized fluid to flow substantially tangentially relative to the surgically prepared working surface. The tangential fluid flow forcibly cleans the surgically prepared working surface of biological fluids and debris.

In accordance with yet another aspect of the invention, an apparatus suitable for cleaning a surgically prepared working surface comprises a body portion adapted to supply pressurized fluid to the surgically prepared working surface and aspirate surface debris dislodged from the surgically prepared working surface. The apparatus further comprises a head portion adapted to confine the supplied pressurized fluid to flow substantially along the surgically prepared working surface to dislodge debris there from when the head portion is in contact with the surgically prepared working surface. The dislodged surface debris are aspirated by the body portion.

In accordance with still another aspect of the invention, an apparatus suitable for cleaning a surgically prepared working surface comprises a body portion adapted to supply pressurized fluid to the surgically prepared working surface and aspirate surface debris dislodged from the surgically prepared working surface. The apparatus further comprises a head portion adapted to constrain the supplied pressurized fluid to flow substantially tangentially relative to the surgically prepared working surface to dislodge debris there from when the head portion is in contact with the surgically prepared working surface. The dislodged surface debris are aspirated by the body portion.

In accordance with a further aspect of the invention, a method for cleaning a surgically prepared working surface comprises supplying pressurized fluid to the surgically prepared working surface, providing at least one surface debris aspirator, constraining the supplied pressurized fluid to flow substantially along the surgically prepared working surface, and using the constrained fluid flow to forcibly clean the surgically prepared working surface of biological fluids and debris.

In accordance with a still further aspect of the invention, a method for cleaning a surgically prepared working surface comprises supplying pressurized fluid to the surgically prepared working surface, providing at least one surface debris aspirator, constraining the supplied pressurized fluid to flow substantially tangentially relative to the surgically prepared working surface, and using the constrained tangential fluid flow to forcibly clean the surgically prepared working surface of biological fluids and debris.

In accordance with another aspect of the invention, an apparatus for cleaning a surgically prepared bone surface comprises a pressurized fluid supply channel; an aspiration channel; and a cleaning head, including at least one chamber, in communication with said aspiration channel and said fluid supply channel. The chamber has an orifice, the boundary of said orifice defining a boundary surface capable of close engagement with the prepared bone surface to substantially close said chamber. The chamber is arranged to create an internal pressure gradient between said pressurized fluid supply channel and said aspiration channel, with a path for fluid flow from the fluid supply channel to the aspiration channel. The fluid flow path for fluid flow includes at least one region in which flow is constrained to flow along the boundary surface.

In accordance with another aspect of the invention, an apparatus for cleaning a surgically prepared bone surface comprises a body portion adapted to supply fluid to the surgically prepared surface and to aspirate surface debris dislodged from the surgically prepared working surface; and a head portion having an orifice adapted to engage the surgically prepared bone surface. The body portion has a length dimension in a lengthwise direction, and the orifice is directed sidewards, in transverse relation to the lengthwise direction of the body portion.

These and other aspects of the invention will become apparent from a review of the accompanying drawings and the following detailed description of the invention.

BRIEF DESCRIPTION OF THE DRAWINGS

The present invention is generally shown by way of reference to the accompanying drawings in which:

FIG. 1 is a front perspective view of an apparatus suitable for cleaning a surgically prepared working surface in accordance with the present invention;

FIG. 1A is an enlarged partial front perspective view of the apparatus of FIG. 1;

FIG. 2 is a side perspective view of the apparatus of FIG. 1 being used to clean a surgically prepared working surface in accordance with the present invention;

FIG. 3 schematically shows an exemplary embodiment of the present invention; and

FIG. 4 is a cross-sectional view taken along the sectioning plane 4-4 of FIG. 2.

DETAILED DESCRIPTION OF THE INVENTION

Some embodiments of the invention will be described in detail with reference to the related drawings of FIGS. 1-4. Additional embodiments, features and/or advantages of the invention will become apparent from the ensuing description or may be learned by practicing the invention.

In the figures, the drawings are not to scale with like numerals referring to like features throughout both the drawings and the description.

The following description is not to be taken in a limiting sense, but is made merely for the purpose of describing the general principles of the invention.

FIG. 1 is a front perspective view of an apparatus or tool generally referred to by reference numeral 10, adapted for cleaning a surgically prepared working surface in accordance with the present invention. The embodiment of FIG. 1 is particularly well adapted for cleaning a substantially planar bony surface, such as is produced by an oscillating saw in preparation for implantation of a knee prosthesis.

The tool 10 includes an elongated body having a sidewards facing orifice 12, situated near the forward end of the body. (“Sidewards” is intended to convey that the orifice faces in a direction generally across or transverse to the long axis or dimension of the body). The forward end of the body, including the orifice, will also be referred to as the “head portion” of the tool 10 The tool preferably has hose couplings, preferably disposed near the rearward end of the tool: a pressurized gas hose connection 14 and a vacuum hose connection 16. Optionally, these connections could be integrated into a trigger type control grip (not shown) which facilitates control of the application/disconnection of both gas and suction, via a simple trigger operated valve. However controlled, gas is controllably supplied under pressure from pressurized gas supply 18 to gas connection 14 via a hose 20. Similarly, suction is controllably supplied from vacuum source 22 via hose 24 to the vacuum hose connection 16.

The head portion 13 of tool 10 is more clearly seen in (magnified) FIG. 1A. Head 13 has an orifice 12 which is preferably bounded by a lip or rim 26. In the embodiment shown, the rim forms a generally square perimeter around the orifice 12. The orifice 12 opens into an internal cavity 26 having a forward chamber 28 and a rearward chamber 30, which are incompletely divided by an internal partition 34. At least one hidden, internal gas channels 36 and 38 connect the rearward chamber to the vacuum hose coupling 24, and thus allow the rearward chamber (vacuum chamber) 30 to communicate with the vacuum supply 22. Similarly, internal pressurized gas channel 40 connects the forward chamber 28 to the pressurized gas connection 14, allowing the forward chamber to communicate with the pressurized gas supply 18.

Forward chamber has an internal barrier 42 which is breached by a wide slot as shown. Optionally, a series of small gas directing holes could be provided to disperse the gas flow into a curtain. Such features tend to spread and direct the gas flow into a ribbon of flowing gas. Further details of the gas flow are discussed below in connection with FIG. 3.

As shown in FIG. 1A, the partition 34 does not extend completely to the plane defined by the rim 26; rather, the partition terminates in a shoulder 46 A small clearance exists between the shoulder 26 and the plane of the rim 26, defining a relatively narrow slot through which gas can flow from the forward chamber to the rearward chamber (thus from pressure toward vacuum).

The entire tool 10 can suitably be machined or otherwise formed from a solid such as aluminum or stainless steel, which are capable of enduring repeated autoclaving for sterilization. Alternatively, polymers or other materials could be used. In some embodiments the tool may be disposable, thereby avoiding the need for sterilization by the hospital.

FIG. 2 shows how the tool can be used to prepare the bony surfaces of a knee to receive a prosthetic replacement. As shown, the bone is previously prepared by cutting with a saw to produce at least one substantially planar cut surface 50. The tool is inserted through an incision, which need not be large, and manipulated to engage the rim 26 with the planar cut, bony surface 50. A close fit is desirable, but some leakage is tolerable. Having the head of the tool engaged with the bony surface 50, the surgeon activates the sources of pressurized gas and suction, and moves the tool in a pattern to clean the bony surface. When the surface is clean (and dry), the surgeon removes the tool and applies the cement in accordance with medical practice. It is recommended that the tool be manipulated from the far side to the near side of the surface, so that debris and blood is pulled from far to near in a scraping motion.

FIG. 3 shows the direction of gas flow when the device is activated in engagement with a bony surface. The bony surface can be visualized as surface 52, but here is imagined to be transparent so as to better visualize the gas flow in the tool. The extent of the rim or other boundary of the orifice defines a boundary surface for the orifice. The figure assumes that the orifice is fully engaged with bony surface 52, by placing with slight pressure the rim 26 flush to the planar bone surface 52. Thus engaged, boundary surface to bony surface, the cavity and bone surface together define a substantially enclosed volume or chamber having a pressurized gas source at one end and a vacuum at the other end, incompletely separated by partition 34. More generally described, the apparatus thus engaged defines a substantially closed volume having on at least one side a bony surface. Due to the pressurized gas source and the vacuum source, the volume has a pressure gradient substantially across the bony surface. The fluid is thus constrained to flow substantially across the surgically prepared surface 52. Most preferably, in at least some region the gradient is substantially tangential to the surface to be cleaned. The fluid is constrained to flow tangentially to the surface to be cleaned, at least in some region.

In a preferred embodiment, the partition 34 constricts or pinches the gas flow, visualized by flow arrows 54 in the figure. Flow between the partition 34 and the bony surface is pinched or constricted as the gas passes through the narrow clearance between partition and bone. Thus, across the narrow sill of partition 34 the flow has increased velocity and decreased pressure due to “Bernoulli's principle” or “venturi effect”. Applicants speculate that the lowered pressure and increased velocity in this pinched channel is efficacious to draw debris and liquid (such as blood) from the interstices of a porous bony surface, which effect is observed to occur with unexpected efficiency.

Gas flow is also visualized in FIG. 4. As the cross section shows, pressurized gas supplied from a source flows forward through an internal channel 40 in the cleaning tool 10 to the forward chamber 28. Simultaneously, suction is applied from vacuum source, which communicated via another internal channel 36 with rearward chamber 30. Due to the pressure gradient, gas flows from the forward chamber to the rearward chamber. However, the complete cavity (comprising forward and rearward chambers 28 and 30) is substantially closed when the orifice is flush against a bony surface, so the gas is constrained to flow through the relatively narrow slot between the lower sill of partition 34 and the top of the bony surface 50. In passing across this lip, the flow accelerates and the pressure drops, drawing fluid and debris off of the surface. Gas, liquid, and debris then flow into the rearward (vacuum) chamber and exit the tool through the vacuum channel, which is preferably large enough to accommodate debris without clogging. The entire cleaning process occurs within a closed volume defined by the combination of the cavity and bony surface in close fitted relationship. In addition to increasing the cleaning efficiency, the closed system also reduces splattering and controls the aerosolization of biological materials (such as blood, fat and marrow).

Although a planar geometry is shown for the orifice, other geometries could be employed for cleaning other surfaces. For example, hemispherical geometries (such as found in socket joints) could be cleaned by a tool with a suitably curved surface, provided that the orifice engage the bony surface to effectively confine the flow and encourage flow across the surface, in a direction generally tangential thereto. Furthermore, cylindrical or conical geometries could be employed to clean bone channels (such as a broached femoral canal).

Note that in the embodiment shown in the figures the tool 10 has a thickness dimension d which is relatively thin in relation to its length L (indicated in FIG. 1). In some embodiments, the thickness d should preferably be less than 12 millimeters, to allow insertion through a relatively small incision. into the interstices of a (prepared) knee joint. More preferably the thickness should be 8 millimeters or less, to service knee joints in a minimally invasive surgical technique. Note also that in the embodiment shown, the orifice or aperture 12 is side facing in relation to the long axis of the tool 10 and the gas and vacuum supply channels included therein. This allows easy access to surfaces having their normal disposed at substantially right angles to the long axis of the tool. This arrangement is advantageous because it considers the geometry of common cutting tools such as either circular or oscillating saws. Such saws cut planes disposed parallel to the plane of the saw's motion. The side facing orifice 12 is conveniently disposed to clean the surfaces produced by such cuts

The inventors presently believe that the preferred pressurized gas for use in the invention is carbon dioxide (CO₂). Some of the reasons for this conclusion are set forth in the Matsen patent, referenced above in the “Background of the Invention”. However, the invention could be modified to employ other pressurized gases, or an admixture of liquid and gas. In order to take full advantage of the “Bernoulli effect” in passing through the constricted channel, a compressible fluid such as a gas or gas mixture is greatly preferred.

A person skilled in the art would undoubtedly recognize that other components and/or configurations may be utilized in the above-described embodiments. Moreover, all terms should be interpreted in the broadest possible manner consistent with the context. In particular, the terms “comprises” and “comprising” should be interpreted as referring to elements, components, or steps in a non-exclusive manner, indicating that the referenced elements, components, or steps may be present, or utilized, or combined with other elements, components, or steps that are not expressly referenced.

While the invention has been described in detail with regards to several embodiments, it should be appreciated that various modifications and/or variations may be made in the invention without departing from the scope or spirit of the invention. In this regard it is important to note that practicing the invention is not limited to the applications described hereinabove. Many other applications and/or alterations may be utilized provided that such other applications and/or alterations do not depart from the intended purpose of the invention. For example, the head, orifice, and rim may be shaped to fit contours other than planar surfaces. Admixtures of gas and liquid may be used in place of a carbon dioxide gas. Various control valves and pressure regulation apparatus may be added to the cleaning head or to it's supply lines. The body may comprise primarily gas and suction lines. The cleaning head may have multiple pressure chambers and/or multiple vacuum chambers; the head could be arranged with suction forward and pressure situated rearward; pressure could be provided in a middle chamber, with gas flowing to two or more suction orifices (one forward, one rear); the pressure could be provided in a middle chamber with suction divided between right and left chambers, causing dual cleaning jets (right and left). Other such variations could be devised. A skirt can be added to or substituted for the rim around the cleaning orifice. A flexible or conformable skirt could be used.

Also, features illustrated or described as part of one embodiment can be used in another embodiment to provide yet another embodiment such that the features are not limited to the exemplary embodiments described hereinabove. Thus, it is intended that the invention cover all such embodiments and variations as long as such embodiments and variations come within the scope of the appended claims and their equivalents. 

1. An apparatus suitable for cleaning a surgically prepared working surface, said apparatus comprising: means for supplying pressurized fluid to the surgically prepared working surface; at least one surface debris aspirator operatively coupled to said pressurized fluid supply means; and means for confining the supplied pressurized fluid to flow substantially along the surgically prepared working surface, said confined fluid flow forcibly cleaning the surgically prepared working surface.
 2. The apparatus of claim 1, wherein the supplied pressurized fluid is carbon dioxide (CO₂) gas, said CO₂ gas being suitable for use on the surgically prepared working surface.
 3. A method for cleaning a surgically prepared working surface, said method comprising the steps of: (a) supplying pressurized fluid to the surgically prepared working surface; (b) providing at least one surface debris aspirator; (c) confining the supplied pressurized fluid to flow substantially along the surgically prepared working surface; and (d) using said confined fluid flow to forcibly clean the surgically prepared working surface.
 4. An apparatus suitable for cleaning a surgically prepared working surface, said apparatus comprising: means for supplying pressurized fluid to the surgically prepared working surface; at least one surface debris aspirator operatively coupled to said pressurized fluid supply means; and means for confining the supplied pressurized fluid to flow substantially tangentially relative to the surgically prepared working surface, said confined tangential fluid flow forcibly cleaning the surgically prepared working surface.
 5. The apparatus of claim 4, wherein the supplied pressurized fluid is carbon dioxide (CO₂) gas, said CO₂ gas being suitable for use on the surgically prepared working surface.
 6. A method for cleaning a surgically prepared working surface, said method comprising the steps of: (a) supplying pressurized fluid to the surgically prepared working surface; (b) providing at least one surface debris aspirator; (c) confining the supplied pressurized fluid to flow substantially tangentially relative to the surgically prepared working surface; and (d) using said confined tangential fluid flow to forcibly clean the surgically prepared working surface.
 7. An apparatus suitable for cleaning a surgically prepared working surface, said apparatus comprising: a body portion adapted to supply pressurized fluid to the surgically prepared working surface and aspirate surface debris dislodged from the surgically prepared working surface; and a head portion adapted to confine the supplied pressurized fluid to flow substantially along the surgically prepared working surface to dislodge debris there from when said head portion is in contact with the surgically prepared working surface, said dislodged surface debris being aspirated by said body portion.
 8. The apparatus of claim 7, wherein the supplied pressurized fluid is carbon dioxide (CO₂) gas, said CO₂ gas being suitable for use on the surgically prepared working surface.
 9. The apparatus of claim 7, wherein the supplied pressurized CO₂ gas flows at a rate suitable for cleaning the surgically prepared working surface from debris.
 10. The apparatus of claim 7, wherein said head portion is adapted to confine the supplied pressurized fluid to flow substantially tangentially relative to the surgically prepared working surface to dislodge debris there from when said head portion is in contact with the surgically prepared working surface, said dislodged surface debris being aspirated by said body portion.
 11. The apparatus of claim 10, wherein the supplied pressurized fluid is carbon dioxide (CO₂) gas, said CO₂ gas being suitable for use on the surgically prepared working surface.
 12. The apparatus of claim 11, wherein the supplied pressurized CO₂ gas flows at a rate suitable for cleaning the surgically prepared working surface from debris.
 13. The apparatus of claim 7, wherein said body portion includes at least one pressurized fluid channel operatively coupled to at least one fluid jet outlet.
 14. The apparatus of claim 13, wherein said body portion further includes at least one surface debris aspirator disposed in operational proximity to said at least one fluid jet outlet.
 15. The apparatus of claim 7, wherein said head portion includes a rim configured to substantially follow the contours of the surgically prepared working surface and at least one partition between said at least one surface debris aspirator and said at least one fluid jet outlet.
 16. The apparatus of claim 15, wherein said at least one partition is sufficiently recessed from said rim to define a constricted flow channel that constrains the supplied jet fluid to flow substantially along the surgically prepared working surface when said rim is in contact with the surgically prepared working surface, said constrained fluid flow sweeping debris from the surgically prepared working surface via said at least one surface debris aspirator.
 17. The apparatus of claim 10, wherein said body portion includes at least one pressurized fluid channel operatively coupled to at least one fluid jet outlet.
 18. The apparatus of claim 17, wherein said body portion further includes at least one surface debris aspirator disposed in operational proximity to said at least one fluid jet outlet.
 19. The apparatus of claim 18, wherein said head portion includes a rim configured to substantially follow the surgically prepared working surface and at least one partition between said at least one surface debris aspirator and said at least one fluid jet outlet.
 20. The apparatus of claim 19, wherein said at least one partition is sufficiently recessed from said rim to constrain the supplied jet fluid to flow substantially tangentially relative to the surgically prepared working surface when said rim is in contact with the surgically prepared working surface, said constrained tangential fluid flow sweeping debris from the surgically prepared working surface via said at least one surface debris aspirator.
 21. An apparatus for cleaning a surgically prepared bone surface, comprising: a pressurized fluid supply channel; an aspiration channel; a cleaning head, including at least one chamber, in communication with said aspiration channel and said fluid supply channel; said chamber having an orifice, the boundary of said orifice defining a boundary surface capable of close engagement with the prepared bone surface to substantially close said chamber; said chamber arranged to create an internal pressure gradient between said pressurized fluid supply channel and said aspiration channel, and having a path for fluid flow from said fluid supply channel to said aspiration channel; wherein said fluid flow path for fluid flow includes at least one region in which flow is constrained to flow along said boundary surface.
 22. The apparatus of claim 21, wherein said fluid flow path comprises at least one slot, whereby said fluid flow is channeled into a sheet of flow.
 23. The apparatus of claim 22, wherein said slot is defined between said boundary surface and a partition which incompletely divides said chamber.
 24. The apparatus of claim 22 wherein said orifice is bounded by a rim.
 25. The apparatus of claim 22 wherein said boundary surface is a substantially plane surface.
 26. The apparatus of claim 22 wherein said boundary surface is a substantially contoured surface.
 27. The apparatus of claim 21, wherein said pressurized fluid supply channel is adapted to supply pressurized carbon dioxide gas.
 28. An apparatus for cleaning a surgically prepared bone surface, comprising: a body portion adapted to supply fluid to the surgically prepared working surface and to aspirate surface debris dislodged from the surgically prepared working surface, said body portion having a length dimension in a lengthwise direction; a head portion having an orifice, adapted to engage the surgically prepared bone surface; said orifice directed sidewards in relation to said lengthwise direction of said body portion.
 29. The apparatus of claim 28, wherein said head portion has a thickness dimension which does not exceed the clearance between a surgically prepared tibia and a surgically prepared femur in a human knee which has been prepared to receive a prosthetic joint replacement.
 30. The apparatus of claim 28, wherein said thickness dimension is 10 millimeters or less. The apparatus of claim 30, wherein said thickness dimension is 8 millimeters or less. The apparatus of claim 28, wherein said orifice is adapted to engage with a substantially planar bone surface.
 31. The apparatus of claim 32, wherein said orifice is surrounded by a rim defining a plane. 